The BPH (benign prostate hyperplasia) patients who have OAB (overactive bladder) after TURP (trans-urethral resection of prostate) or PVP (photoselective vaporization of prostate) will participate in this study. The subjects will be randomized 1:1 to the solifenacin succinate group or to the placebo treatment group. The subjects shall take investigational product each night before sleeping from for four weeks and complete voiding diary. At Week-2 and Week-4 of the treatment, the subjects will be asked to complete the following activities: physical exam, vital signs test, IPSS, OABSS, post-void residual (PVR) test, and uroflowmetry, and will be asked to answer the BSW, (Benefit, Satisfaction and Willingness to Continue Questions) questionnaire.